An outliner (or outline processor) is a specialized type of text editor (word processor) used to create and edit outlines, which are text files which have a tree structure, for organization. Textual information is contained in discrete sections called "nodes", which are arranged according to their topic–subtopic (parent–child) relationships, sort of like the members of a family tree. When loaded into an outliner, an outline may be collapsed or expanded to display as few or as many levels as desired.
Outliners are used for storing and retrieving textual information, with terms, phrases, sentences, or paragraphs attached to a tree. So rather than being arranged by document, information is arranged by topic or content. An outline in an outliner may contain as many topics as desired. This eliminates the need to have separate documents, as outlines easily include other outlines just by adding to the tree.
The main difference between a hand-written outline and a digital one is that the former is usually limited to a summary or blueprint of a planned document, while the latter may easily include all of the content of the entire document and many more. In other words, as a hand-written work an outline is a writing tool, but on a computer, it is a general purpose format supported by a robust development and display medium capable of handling knowledge from its creation to its end use.
Outliners may be used in content creation instead of general word processors for capturing, organizing, editing, and displaying knowledge or general textual information. Outliners are ideal for managing lists, organizing facts and ideas, and for writing computer programs. They are also used for goal and task management (including personal information management and project management), and for writing books and movie scripts.
The principal attribute of outline editors is that they support or enforce the use of a hierarchy of their items.
- Editing: Sound parent-child relationships are enforced when the user modifies the document structure. For example:
- Promoting, demoting, copying, or deleting a parent has the same effect on the children.
- Every item entry must be within one level of its predecessor, such that each item must be a sibling or child of the preceding item (thus, no item can be a grandchild of the preceding item).
- Viewing: The tool enables the user to affect the display by level. For example:
- Applying styles by outline level (e.g., bold all 1st level items).
- Displaying selected levels (e.g., show all 1st and 2nd level items, but none deeper).
- Lifting an entire section out to work on it in isolation, ignoring everything else during that editing, then dropping it back into place (known as hoisting and de-hoisting).
- Search/Filter: The tool displays only items that contain the query terms plus their ancestors (parent, grandparent...) to give them context.
- File import and export: Both the content and structure of outlines are conveyed when files are imported or exported (e.g., from and to tab-indented files).
- Fields/Columns: Items can also have additional fields of information. This data can be shown as columns of data in the outline or as fields in the second pane (see 'Layout' below). Some outliners also allow the user to create custom fields and/or filter on fields.
There are two basic types of outliners: one-pane or intrinsic, and two-pane or extrinsic, each with its strengths and weaknesses.
A one-pane outliner is known as an intrinsic outliner because the text itself is organized into an outline format—individual sections (such as paragraphs) of text can be collapsed or expanded, while keeping others in view. Everything is displayed within a single area, hence the term one pane. One of the strengths of one-pane outliners is that, because the text itself is what is structured and because several nodes of text are visible at once, it is easy to edit across sections. The drawback is that, because the structure is not always visible, there is not as strong an overview of the whole or ability to quickly navigate between sections as with a two-pane outliner. Some word processors, such as Microsoft Word, have an Outline Mode to help with structuring documents.
A two-pane outliner separates structure from content—the structure is extrinsic to the text. A tree structure with node titles is presented in one pane, and the text is shown in another. Since the structure is always clearly shown at all times separately from content, this format allows for a quick overview of the structure, and easy navigation. The drawback is that since only one node's worth of text is shown at one time and navigation has the additional step of crossing panes, the structure is more rigid, making editing across nodes more difficult. This view is similar to many file browsers and email programs (which can be thought of as three-pane outliners). This type of structure is useful also as a document management tool where the second pane is a document in place of textual information.
A one- and two-pane outliner may be combined as a hybrid. This allows multiple notes' text and graphics to be shown at the same time. The organizational power of outline in hybrid is in the parent outline structure, not in the second pane text, making it a very effective structure for topical organization. One additional advantage of hybrid is that single pane can be used as single pane outliner with second pane used for notes or reference tracking.
A third approach to intrinsic outlines is the multi-column outliner. It is similar to the one-pane outliner in that the text itself is organized into an outline format. However, the text sections do not collapse or expand, and all sections are visible but held in a separate column (one for each level). This approach allows structure and content to be visible at the same time.
Several file formats support an outline structure natively or encourage the use/creation of outline structures.
- XML - XML's purpose is to aid information systems in sharing structured data
- HTML/XHTML - outlines relatively trivial thanks to nested markup
- OPML - simple XML-based format designed for outlines, but also used for syndication feedlists
- OML - alternative to OPML
- RDF - (various formats) has web-oriented node & arc graph model, a subset can be used for outline
- XOXO - dedicated HTML-based microformat for outlines
- CHM - standard Windows format for help, books, etc.
List of outliners
|Acta||Mac OS 9||Single pane outliner, free to download|
|ActionOutline||Windows||Double-pane outliner. Multiple outlines per file, selected via 'worksheet-style' tabs.|
|AllMyNotes Organizer||Windows||Can password-protect file access, supports skins. Free and Portable editions available.|
|Aml Pages||Windows||Outliner support of notes tree.|
|Bonsai||Windows||(Desktop Edition) Designed to synchronise with the Palm OS version of Bonsai|
|Brainstorm||Windows||trial edition available|
|CherryTree||Windows/Linux||Freeware. Manage, edit and take notes. Portable version also available|
|Circus Ponies NoteBook||Mac OS X||Single-pane outliner designed to resemble a spiral bound notebook|
|Code Browser||Windows/Linux||folding text editor, can outline source code|
|Correlate||Windows||folding text Knowledge Map (K-Map)Collect, organize, outline, share and archive files, email, documents and URL's. Content can be embedded, moved and transformed to PDF's. The outline can be presented directly in SharePoint.|
|Deep Notes||Mac OS X||Freeware single pane outliner. Only 1.7 megabytes, runs on OS X 10.4 or later.|
|Ecco Pro||Windows||Freeware outliner. Support subscription. EccoMV add-on for RTF pane.|
|Fargo||HTML 5||Online outliner with Dropbox storage|
|Flashnote||Windows / Linux||Freeware outliner with support of notes tree|
|Foldout||Windows||Freeware single-pane outliner.|
|GrandView||MS-DOS||Single-pane outliner dating from the 1980s. No longer supported. Clone feature.|
|Hiero Outliner||Linux (Ubuntu/Debian)||Single pane outliner for x86 systems. Multiple outlines in the same window, selected by tabs. Tree lines & color bars can be toggled on/off.|
|hnb||Linux/platform independent||Terminal based outliner|
|Idea Cruncher||Windows||Minimalist two-pane outliner|
|Idea Rover||Windows||Research paper outliner|
|In Control||Mac OS 7/8||Vintage outliner from Attain Corp, which could sort or filter outlines according to keywords or metadata attached to each topic.|
|InfoQube||Windows||Two-pane outliner with custom columns, rich-text formatting, and several concepts based on EccoPro.|
|Inspiration||Windows / Mac OS||Visual brainstorming with idea maps combined with text based outlining.|
|Jot+ Notes||Windows||Two-pane outliner where the 2nd pane supports Rich Text formatting and embedded pictures and objects, such as spreadsheets. One can navigate not only via the topic hierarchy in pane one, but also via hyperlinks in the text of pane two.|
|Jreepad||Platform independent||Compatible with Treepad. Written in Java.|
|KAMAS||CP/M, later MS-DOS||(Knowledge and Mind Amplification System) Not as successful for MS-DOS as it had been for CP/M. Limited export capability.|
|KeepNote||Windows/Linux/MacOS||Notes saved in HTML. Written in Python.|
|KeyNote||Windows||Mozilla Public License. No longer supported.|
|KeyNoteNF||Windows||Mozilla Public License. Evolution of KeyNote.|
|Leo||Windows/Linux/MacOS||Text editor with outlines; remarkably flexible tree structure. Written in Python using Qt.|
|Maxthink||Windows 2000, ME, XP, Vista, 7, 8||Venerable MSDOS outliner now in Windows|
|MemPad||Windows||Plain text two-pane outliner. Freeware, portable, flexible, small.|
|MORE||Mac OS 7/8/9||Classic Mac outliner from the late 1980s & early 1990s|
|MSD Organizer||Windows||Single-pane outliner in the following modules: Contacts, Cards, Budget, Property, Health and Music.|
|MyInfo||Windows||Two-pane, but can emulate basic one-pane outliner as well.|
|myBase||Windows||Tree-based free-form outliner and database system with three panes.|
|Neomem||Windows||Three-pane outliner. Website last updated July 2008.|
|Nethnic Pandora||Windows||Tree-based text editor and project management tool|
|NoteCase||Windows/Linux/MacOS||No longer supported.|
|NoteKeeper||Windows||Lightweight freeware two-pane outliner|
|Noteliner||Windows||Lightweight freeware outliner with "to do" capabilities, tagging & tables|
|NoteMap||Windows||No longer sold as of January 1, 2015|
|OneModel||cross-platform||Free/open: record, manage and share any knowledge at an atomic level. High efficiency for GDT, note-takers, technologists.|
|Outline||Mac OS X||Digital notebook for private and business use.|
|OutlineEdit||Mac OS X||Simple outliner that supports tags in the form of 'Categories'.|
|OutWiker||cross-platform||Desktop wiki and outliner. Notes are stored as a directory tree on disk.|
|OmniOutliner||Mac OS X||Single/double pane outliner with columns and extensive customization capabilities.|
|Opal||Mac OS X||Single pane outliner, essentially a port of 'Acta' to Mac OS X|
|OrgMode||cross-platform||Emacs outlining mode|
|Outliner Lighto||Windows||Free software, console-based outliner written in FreePascal|
|Redhaven Outline||Windows||Lightweight freeware two-pane outliner|
|Scrivener||Mac OS & Windows; Linux beta||Flexible content generator for writers; powerful multipane outliner|
|Sense||Windows||Outliner supporting a Writing Workflow with Citation and Bibliography.|
|SEO Note||Windows||Free lightweight two-pane outliner|
|STAR My Data Safe||Mac OS X, Windows||Outliner with built-in data encryption; shareware|
|TheBrain||Windows, Mac, Linux, iOS, Android||Free form graphical outliner|
|The Guide||Windows||Free lightweight two-pane outliner|
|ThinkTank||MS-DOS||Early PC outliner, now abandonware|
|Tines||Mac, Linux||GPL Console-based outliner, evolution of hnb with improved organizer/calendar functionality|
|Tkoutline||Platform independent||Written in Tcl/Tk|
|ToDoList||Windows||Free (Eclipse Public License). Portable. Large number of node attributes. French and Spanish versions.|
|Tombo||Windows, Windows CE, Windows Mobile||Minimalistic. Regex search. GPLv2.|
|Total Text Container||Windows||Freeware 2-pane outliner|
|Tree||Mac OS X||A lightweight, horizontally expanding outliner that exports to many formats.|
|Treeline outliner||Windows/Linux||Free 3-pane outliner; 2nd pane shows details of highlighted node, 3rd pane lists details of its children.|
|Treepad||Windows/Linux||Two-pane outliner. Free and paid versions.|
|Treesheets||Windows/Linux/Mac OS X||Unique open-source program; the hybrid of a spreadsheet and a single pane outliner.|
|TuxCards||Linux||Freeware 2-pane outliner|
|The Vim Outliner||cross-platform||Vim plugin|
|UV Outliner||Windows||Free, single pane outliner. Unsupported. Last update October 2012.|
|Vault 3||Windows, Linux, Mac OS X, Android||Free outliner. XML import and export. PDF export. Optional 128-bit AES encryption.|
|Vim Outliner||cross-platform||Vim plugin|
|VOoM||cross-platform||Vim plugin, emulates two-pane outliner. Requires Python and Vim compiled with Python interface.|
|Wanderlust||Windows||A basic open-source outliner|
|XLnotes||Windows||Microsoft Excel add-in that allows to take notes which contain Word documents, web pages and attachments. Emulates two-pane free form outliner.|
Mobile device outliners
|Android Outliner||Android||Sync Google Tasks, Treepad, OPML (e.g. OmniOutliner for Mac and Fargo, if you save in OPML) and Natara Bonsai via USB or DropBox; opens Outlines with Dropbox, ownCloud, BoxCryptor; due-date based filtering; supports multiple outlines. Under active development, with very user feedback-driven feature selection.|
|BeSharp||Android||Simple and intuitive interface, free.|
|BeSharp for iOS||iOS||Simple and intuitive interface, incorporates Pomodoro technique and GTD/ZTD.|
|CarbonFin Outliner||iOS||Outliner for iPhone, iPod touch, and iPad. Web app with synchronization is also available.|
|Circus Ponies NoteBook for iPad||iOS||Port of Circus Ponies NoteBook to the iPad.|
|Cotton Notes||iOS||Outliner for iOS devices, providing support for markdown, attachments, and collaboration|
|Grapevine for Android||Android||Outliner for Android devices (Android 2.2 and later). Continuous entry mode for efficient data entry.|
|Halna Outliner||Android||2-pane outliner for Android. Customizable UI, simple, efficient. Ad-supported.|
|Inspiration Maps||iOS||Visual brainstorming with idea maps combined with text based outlining.|
|NoteLynX||Android||Features Multiple Parents and Cross Reference links between notes.|
|OmniOutliner for iPad||iOS||Port of OmniOutliner to iPad.|
|Outline||iOS||Digital notebook for private and business use.|
|Outline Pro for iPad||iOS||Special outliner for writers and students. Ideal for papers, essays and speeches.|
|Tree Note||Android||Outliner for Android devices. (Android 2.2 and later).|
|Vault 3 for Android||Android||Outliner for Android devices (Android 2.1 or later). Desktop versions are also available (Windows, Linux, and Mac OS X).|
|Zeptoliner||iOS||Outliner for iPhone and iPod Touch.|
This table shows a list of browser-based outliners categorised by the functionality that they provide (see 'Design' above). Browser-based outliners run inside a desktop or mobile web browser (smart phone or tablet) and may synchronise the outline's data with a remote server or store it locally on the user's device.
|Name||Promote/ demote||Clone||Styling||Expose/ hide levels||Hoist||Search||Import OPML||Export OPML||Export other||Collaboration||Files|
|The Outliner of Giants||Yes||Yes||Yes||Yes||Yes||Yes||Yes||Yes||Yes||Yes||Yes|
- Code folding
- Folding editor
- Desktop Wiki
- Personal information manager
- Personal knowledge base
- Concept mapping
- Robert S. Houghton (2005-12-31). "Outlining Tutorial for Microsoft Word". Ceap.wcu.edu. Retrieved 2009-02-18.
- "How to create an outline in a document in a Word 2002". Support.microsoft.com. 2006-07-27. Retrieved 2009-02-18.
- "Overview of Windows Outliners". John.redmood.com. Retrieved 2009-02-18.